Overview of fitness to fly

Medical emergencies during flights are uncommon (they occur in 1 of every 604 flights). The most common in-fight medical problems reported are syncope or presyncope (37.4%), respiratory symptoms (12.1%), nausea or vomiting (9.5%), and cardiac symptoms (7.7%). Physicians may be asked to assess and provide care to a passenger having a medical emergency on a commercial flight. Few in-flight medical emergencies result in diversion of the aircraft or patient death. The final decision to redirect the flight lies with the captain of the aircraft and is made after considering advice from the medical provider on board or clinicians at ground-based medical consultation services.

Air travel can pose significant risks to people with certain medical conditions. Medical clearance is usually required by the airline if the passenger:

  • suffers from any disease that is believed to be actively contagious and communicable
  • is likely to be a hazard or cause discomfort to other passengers because of their physical or behavioural condition
  • is considered to be a potential risk to the safety or punctuality of the flight including the possibility of diversion or an unscheduled landing
  • is incapable of caring for themselves and requires special assistance
  • has a medical condition which may be adversely affected by the flight environment.

Passengers who do not fall into the above categories usually do not need medical clearance; however, consult the airline if there is any doubt about whether medical clearance is required. It is advisable to contact the relevant airline well in advance of travel.

Requirements for medical clearance can differ between airlines; airlines produce their own travel clearance guidelines, which are available online. An example of information available online can be found on the Qantas website.

Further information can be found in the International Air Transport Association (IATA) medical manual, available here.

Commercial aircrafts usually cruise at altitudes between 10 000 and 13 500 metres (32 800 and 44 300 feet). Pressurisation of the cabin ensures that the pressure corresponds to an altitude of no more than 2438 metres (8000 feet), which generates a cabin air pressure of 565 mmHg. In this environment, haemoglobin oxygen saturation normally remains above 90% in the average healthy person, and partial pressure of inspired oxygen (PiO2) falls to the equivalent of breathing 15.1% oxygen at sea level (normally 20.8%). These changes create a mild hypoxia, which is usually well tolerated by a healthy person. The reduced cabin pressure also causes expansion of gas by about one-third, which can be important if there is trapped gas in closed body cavities (eg sinuses, middle ear, pleural cavity).

Other features of commercial air travel that might cause problems are:

  • dryness of air in cabin
  • reduced mobility of travellers, potentially causing venous thromboembolism (see VTE prophylaxis for long-distance travel)
  • close proximity to other people and consequent risk of respiratory tract infections
  • disturbance of circadian rhythms on longer flights (see Jet lag).